Subject: [PATCH v3] mailinfo: fix pointential memory leak if `decode_header` failed

From: "Lidong Yan via GitGitGadget" <[email-masked]>
Date: Mon, 12 May 2025 16:17:07 +0000

From: Lidong Yan <[email-masked]>

In mailinfo.c:decode_header, if convert_to_utf8 failed, the strbuf stored
in dec will leak. Simply add strbuf_release and free(dec) will solve
this problem.

Signed-off-by: Lidong Yan <[email-masked]>
---
    decode_header: fix pointential memory leak if decode_header failed
    
    In mailinfo.c line 539, if convert_to_utf8 failed, the strbuf stored in
    dec will leak. Simply add strbuf_release and free(dec) will solve this
    problem.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1956%2Fbrandb97%2Ffix-mailinfo-decode-header-leak-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1956/brandb97/fix-mailinfo-decode-header-leak-v3
Pull-Request: https://github.com/git/git/pull/1956

Range-diff vs v2:

 1:  90dc9b0d49b ! 1:  7f8ce472750 mailinfo: fix pointential memory leak if `decode_header` failed
     @@ mailinfo.c: static void decode_header(struct mailinfo *mi, struct strbuf *it)
       			goto release_return;
       		case 'b':
      -			dec = decode_b_segment(&piecebuf);
     -+			if ((found_error = decode_b_segment(&dec, &piecebuf))) {
     ++			if ((found_error = decode_b_segment(&dec, &piecebuf)))
      +				goto release_return;
     -+			}
       			break;
       		case 'q':
      -			dec = decode_q_segment(&piecebuf, 1);
     -+			if ((found_error = decode_q_segment(&dec, &piecebuf, 1))) {
     ++			if ((found_error = decode_q_segment(&dec, &piecebuf, 1)))
      +				goto release_return;
     -+			}
       			break;
       		}
      -		if (convert_to_utf8(mi, dec, charset_q.buf))
      +		if (convert_to_utf8(mi, &dec, charset_q.buf)) {
     -+			strbuf_release(&dec);
       			goto release_return;
      +		}
       
     @@ mailinfo.c: static void decode_header(struct mailinfo *mi, struct strbuf *it)
       		in = ep + 2;
       	}
       	strbuf_addstr(&outbuf, in);
     +@@ mailinfo.c: release_return:
     + 	strbuf_release(&outbuf);
     + 	strbuf_release(&charset_q);
     + 	strbuf_release(&piecebuf);
     ++	strbuf_release(&dec);
     + 
     + 	if (found_error)
     + 		mi->input_error = -1;
      @@ mailinfo.c: static int is_inbody_header(const struct mailinfo *mi,
       
       static void decode_transfer_encoding(struct mailinfo *mi, struct strbuf *line)
       {
      -	struct strbuf *ret;
     -+	struct strbuf ret;
     -+	int found_error = 0;
     ++	struct strbuf ret = STRBUF_INIT;
       
       	switch (mi->transfer_encoding) {
       	case TE_QP:
      -		ret = decode_q_segment(line, 0);
     -+		found_error = decode_q_segment(&ret, line, 0);
     ++		decode_q_segment(&ret, line, 0);
       		break;
       	case TE_BASE64:
      -		ret = decode_b_segment(line);
     -+		found_error = decode_b_segment(&ret, line);
     ++		decode_b_segment(&ret, line);
       		break;
       	case TE_DONTCARE:
       	default:
     @@ mailinfo.c: static int is_inbody_header(const struct mailinfo *mi,
      -	strbuf_release(ret);
      -	free(ret);
      +	strbuf_addbuf(line, &ret);
     -+	if (!found_error)
     -+		strbuf_release(&ret);
     ++	strbuf_release(&ret);
       }
       
       static inline int patchbreak(const struct strbuf *line)

 mailinfo.c | 39 ++++++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 19 deletions(-)

diff --git a/mailinfo.c b/mailinfo.c
index 7b001fa5dbd..9bda2e8170f 100644
--- a/mailinfo.c
+++ b/mailinfo.c
@@ -381,11 +381,11 @@ static int is_format_patch_separator(const char *line, int len)
 	return !memcmp(SAMPLE + (cp - line), cp, strlen(SAMPLE) - (cp - line));
 }
 
-static struct strbuf *decode_q_segment(const struct strbuf *q_seg, int rfc2047)
+static int decode_q_segment(struct strbuf *out, const struct strbuf *q_seg,
+			    int rfc2047)
 {
 	const char *in = q_seg->buf;
 	int c;
-	struct strbuf *out = xmalloc(sizeof(struct strbuf));
 	strbuf_init(out, q_seg->len);
 
 	while ((c = *in++) != 0) {
@@ -405,15 +405,14 @@ static struct strbuf *decode_q_segment(const struct strbuf *q_seg, int rfc2047)
 			c = 0x20;
 		strbuf_addch(out, c);
 	}
-	return out;
+	return 0;
 }
 
-static struct strbuf *decode_b_segment(const struct strbuf *b_seg)
+static int decode_b_segment(struct strbuf *out, const struct strbuf *b_seg)
 {
 	/* Decode in..ep, possibly in-place to ot */
 	int c, pos = 0, acc = 0;
 	const char *in = b_seg->buf;
-	struct strbuf *out = xmalloc(sizeof(struct strbuf));
 	strbuf_init(out, b_seg->len);
 
 	while ((c = *in++) != 0) {
@@ -447,7 +446,7 @@ static struct strbuf *decode_b_segment(const struct strbuf *b_seg)
 			break;
 		}
 	}
-	return out;
+	return 0;
 }
 
 static int convert_to_utf8(struct mailinfo *mi,
@@ -475,7 +474,7 @@ static int convert_to_utf8(struct mailinfo *mi,
 static void decode_header(struct mailinfo *mi, struct strbuf *it)
 {
 	char *in, *ep, *cp;
-	struct strbuf outbuf = STRBUF_INIT, *dec;
+	struct strbuf outbuf = STRBUF_INIT, dec = STRBUF_INIT;
 	struct strbuf charset_q = STRBUF_INIT, piecebuf = STRBUF_INIT;
 	int found_error = 1; /* pessimism */
 
@@ -530,18 +529,20 @@ static void decode_header(struct mailinfo *mi, struct strbuf *it)
 		default:
 			goto release_return;
 		case 'b':
-			dec = decode_b_segment(&piecebuf);
+			if ((found_error = decode_b_segment(&dec, &piecebuf)))
+				goto release_return;
 			break;
 		case 'q':
-			dec = decode_q_segment(&piecebuf, 1);
+			if ((found_error = decode_q_segment(&dec, &piecebuf, 1)))
+				goto release_return;
 			break;
 		}
-		if (convert_to_utf8(mi, dec, charset_q.buf))
+		if (convert_to_utf8(mi, &dec, charset_q.buf)) {
 			goto release_return;
+		}
 
-		strbuf_addbuf(&outbuf, dec);
-		strbuf_release(dec);
-		free(dec);
+		strbuf_addbuf(&outbuf, &dec);
+		strbuf_release(&dec);
 		in = ep + 2;
 	}
 	strbuf_addstr(&outbuf, in);
@@ -552,6 +553,7 @@ release_return:
 	strbuf_release(&outbuf);
 	strbuf_release(&charset_q);
 	strbuf_release(&piecebuf);
+	strbuf_release(&dec);
 
 	if (found_error)
 		mi->input_error = -1;
@@ -634,23 +636,22 @@ static int is_inbody_header(const struct mailinfo *mi,
 
 static void decode_transfer_encoding(struct mailinfo *mi, struct strbuf *line)
 {
-	struct strbuf *ret;
+	struct strbuf ret = STRBUF_INIT;
 
 	switch (mi->transfer_encoding) {
 	case TE_QP:
-		ret = decode_q_segment(line, 0);
+		decode_q_segment(&ret, line, 0);
 		break;
 	case TE_BASE64:
-		ret = decode_b_segment(line);
+		decode_b_segment(&ret, line);
 		break;
 	case TE_DONTCARE:
 	default:
 		return;
 	}
 	strbuf_reset(line);
-	strbuf_addbuf(line, ret);
-	strbuf_release(ret);
-	free(ret);
+	strbuf_addbuf(line, &ret);
+	strbuf_release(&ret);
 }
 
 static inline int patchbreak(const struct strbuf *line)

base-commit: 6f84262c44a89851c3ae5a6e4c1a9d06b2068d75
-- 
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